JP2003301066A - Lightweight structural material and thermal insulation with good degradability when scrapped and manufacturing method thereof - Google Patents

Lightweight structural material and thermal insulation with good degradability when scrapped and manufacturing method thereof

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Publication number
JP2003301066A
JP2003301066A JP2002108950A JP2002108950A JP2003301066A JP 2003301066 A JP2003301066 A JP 2003301066A JP 2002108950 A JP2002108950 A JP 2002108950A JP 2002108950 A JP2002108950 A JP 2002108950A JP 2003301066 A JP2003301066 A JP 2003301066A
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JP
Japan
Prior art keywords
resin
foam
polylactic acid
melting point
extruder
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
JP2002108950A
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Japanese (ja)
Other versions
JP4299490B2 (en
Inventor
Takaaki Hirai
孝明 平井
Hiroyuki Tarumoto
裕之 樽本
Shinichi Anami
伸一 阿南
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sekisui Kasei Co Ltd
Original Assignee
Sekisui Plastics Co Ltd
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Priority to JP2002108950A priority Critical patent/JP4299490B2/en
Publication of JP2003301066A publication Critical patent/JP2003301066A/en
Application granted granted Critical
Publication of JP4299490B2 publication Critical patent/JP4299490B2/en
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Abstract

<P>PROBLEM TO BE SOLVED: To provide an environmentally friendly structural material made of a synthetic resin having good mechanical strength and heat insulating properties, in which the material becomes harmless by natural degradation when scrapped, is uniformly foamed to a high expansion ratio of at least ten times and has a low open-cell ratio of 20% or less. <P>SOLUTION: In this structural material, a poly(lactic acid)-based resin of a melting point of 110-170°C that is prepared by copolymerization of D-lactic acid and L-lactic acid at a ratio in which one lactic acid is 2-10% and the other is 98-90%, and, as a foaming agent, an aliphatic ether, are used. The structural material is made of a resin foam that is extruded at a lower temperature than the melting point of poly(lactic acid) resin, is expanded to 10 times or more and has an open-cell ratio of 20% or less. <P>COPYRIGHT: (C)2004,JPO

Description

【発明の詳細な説明】Detailed Description of the Invention

【０００１】[0001]

【産業上の利用分野】この発明は、遺棄分解性の良好な
軽量構造材及びその製造方法に関するものである。とく
に、この発明は、大気下又は土壌中に遺棄すると自然に
分解して無害なものとなる特性を持ち、且つ常温付近で
すぐれた機械的強度及び／又は熱絶縁性とを持った構造
材に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lightweight structural material having good abandonment and decomposability and a method for producing the same. In particular, the present invention relates to a structural material that has the property of naturally decomposing and becoming harmless when it is abandoned in the air or in the soil, and has excellent mechanical strength and / or thermal insulation at around room temperature. It is a thing.

【０００２】[0002]

【従来の技術】スチレン系樹脂で作られた発泡体は、包
装材、緩衝材、魚箱、保冷箱、壁パネル等として広く使
用されている。これは、スチレン系樹脂が高い倍率で均
一に容易に発泡させることができ、得られた発泡体が比
較的耐候性が良好で強度も大きく、その上に連続気泡率
が低くて熱絶縁性が良好だからである。BACKGROUND OF THE INVENTION Foams made of styrene resin are widely used as packaging materials, cushioning materials, fish boxes, cold storage boxes, wall panels and the like. This is because the styrene resin can be easily and uniformly foamed at a high magnification, the obtained foam has relatively good weather resistance and high strength, and in addition, the open cell ratio is low and the thermal insulation property is low. Because it is good.

【０００３】スチレン系樹脂の発泡体は、成形品として
その用途に供さられた後は、回収された後、減容処理さ
れ、リサイクル原料として新たに再利用されたりしてい
る。リサイクルという点では省資源に貢献しているとい
える。[0003] Styrene-based resin foams are used as molded articles for their uses, and then recovered, subjected to volume reduction treatment, and reused as a recycled raw material. It can be said that it contributes to resource saving in terms of recycling.

【０００４】他方、ポリ乳酸系樹脂は生分解し易い樹脂
として知られている。従って、ポリ乳酸系樹脂は、スチ
レン系樹脂とは異なり、使用後の処理として別の方法を
与える選択肢の一つとして、念頭に浮かぶ樹脂である。
ところが、ポリ乳酸系樹脂は以下に述べるように、スチ
レン系樹脂とは大きく性質を異にしており、発泡させに
くい樹脂である。On the other hand, polylactic acid resins are known as resins that are easily biodegradable. Therefore, unlike the styrene-based resin, the polylactic acid-based resin is a resin that comes to mind as one of options to give another method as a treatment after use.
However, as will be described below, the polylactic acid-based resin has a property greatly different from that of the styrene-based resin and is a resin that is difficult to foam.

【０００５】ポリ乳酸系樹脂は、乳酸が重合又は共重合
したものである。乳酸はスチレンと違って、分子中に不
斉炭素原子を含んでいる。このために、乳酸は光学的活
性を示す。従って、乳酸にはＤ−体、Ｌ−体及びラセミ
体（Ｄ−体とＬ−体との等量混合物）の３種のものが存
在する。それゆえ、乳酸を重合させて得られたポリ乳酸
は、これら３種のものの混合割合と重合方法の相違など
によって、色々と性質の異なった重合体を生じる。事
実、ポリ乳酸系樹脂には結晶性のものから非晶性のもの
まで、色々と異なったグレードのものがあり、融点又は
軟化点も区々である。The polylactic acid type resin is obtained by polymerizing or copolymerizing lactic acid. Unlike styrene, lactic acid contains an asymmetric carbon atom in its molecule. Because of this, lactic acid exhibits optical activity. Therefore, there are three kinds of lactic acid, which are D-form, L-form and racemic form (equal mixture of D-form and L-form). Therefore, the polylactic acid obtained by polymerizing lactic acid produces polymers having different properties depending on the mixing ratio of these three types and the difference in the polymerization method. In fact, there are various different grades of polylactic acid-based resin, from crystalline to amorphous, and their melting points or softening points are also different.

【０００６】一般にポリ乳酸系樹脂は、これを加熱する
と、軟化又は溶融して、すぐに粘度の低い液体となる。
従って、ポリ乳酸系樹脂は、これを加熱したとき発泡に
適した溶融粘度を示す温度範囲が極めて狭い。このため
に、ポリ乳酸系樹脂は、これを加熱して発泡に適した状
態を発現させることが困難であり、従って発泡させにく
い樹脂とされている。Generally, when a polylactic acid resin is heated, it softens or melts and immediately becomes a liquid having a low viscosity.
Therefore, the polylactic acid resin has an extremely narrow temperature range in which it exhibits a melt viscosity suitable for foaming when heated. For this reason, it is difficult for the polylactic acid-based resin to develop a state suitable for foaming by heating the polylactic acid-based resin, and thus it is considered as a resin that is difficult to foam.

【０００７】そこで、ポリ乳酸系樹脂を変性して発泡さ
せ易くしようとの試みがなされた。例えば特開平８−１
９８９９２号公報は、ポリ乳酸系樹脂が弾性と復元性と
に乏しく、また耐衝撃性に劣るとして、乳酸の構造単位
と他のポリエステル構造単位との共重合体として、この
共重合体を押出発泡することを提案している。他のポリ
エステル構造単位としては、例えばコハク酸とエチレン
グリコールとの脱水縮合したものを使用することとして
いる。この公報は８倍に発泡した発泡体が得られたと記
載しているが、この発泡倍率は低くて満足なものではな
い。その上に、この提案のように、他のポリエステル構
造単位を導入したのでは、得られた共重合体がポリ乳酸
系樹脂の生分解性を低下させたものとなってしまい満足
なものにならない。Therefore, attempts have been made to modify the polylactic acid resin to facilitate foaming. For example, JP-A-8-1
No. 98992 discloses that a polylactic acid-based resin has poor elasticity and resilience, and also has poor impact resistance, and this copolymer is extruded and foamed as a copolymer of a lactic acid structural unit and another polyester structural unit. I suggest you do. As another polyester structural unit, for example, a dehydration-condensation product of succinic acid and ethylene glycol is used. Although this publication describes that a foam expanded to 8 times was obtained, this expansion ratio is low and not satisfactory. In addition, if other polyester structural units are introduced as in this proposal, the copolymer obtained is one in which the biodegradability of the polylactic acid-based resin is reduced, which is not satisfactory. .

【０００８】また、特開２０００−７８１５号公報は、
ポリ乳酸系樹脂の溶融粘度を上昇させるために、ポリ乳
酸系樹脂に増粘剤を加えて押出発泡させることを提案し
ている。増粘剤としては有機及び無機の広汎な化合物が
使用できると記載されているが、その中には明らかにポ
リ乳酸系樹脂を生分解し難くするものが多く含まれてい
る。従ってこの提案によったのでは、得られた発泡体が
生分解性の劣るものとなるだけでなく、連続気泡率の高
いものとなって、機械的強度や断熱性の良好なものとは
ならない。Further, Japanese Patent Laid-Open No. 2000-7815 discloses
In order to increase the melt viscosity of the polylactic acid resin, it has been proposed to add a thickener to the polylactic acid resin and perform extrusion foaming. It is described that a wide variety of organic and inorganic compounds can be used as the thickener, but among them, there are many that clearly make the polylactic acid resin difficult to biodegrade. Therefore, according to this proposal, not only the obtained foam becomes inferior in biodegradability, but also the open cell ratio becomes high and the mechanical strength and the heat insulating property are not good. .

【０００９】[0009]

【発明が解決しようとする課題】この発明は、遺棄する
と自然に分解して無害なものとなるような構造材で、少
なくとも１０倍以上の高い倍率に均一に発泡して連続気
泡率が低くて２０％以下であり、従って良好な機械的強
度と断熱性とを持った構造材を提供しようとするもので
ある。また、環境にやさしい断熱材を提供しようとする
ものである。SUMMARY OF THE INVENTION The present invention is a structural material which, when abandoned, spontaneously decomposes and becomes harmless, and is uniformly foamed at a high magnification of at least 10 times or more to have a low open cell ratio. It is 20% or less, and therefore, an attempt is made to provide a structural material having good mechanical strength and heat insulating properties. It also seeks to provide environmentally friendly insulation.

【００１０】[0010]

【課題解決のための手段】この発明者は、上述の課題の
うち、遺棄分解性の良好な構造材を得るためには、ポリ
乳酸系樹脂を使用するのが適していると考えた。そこ
で、色々なグレードのポリ乳酸系樹脂を用い、これを押
出機に入れて溶融し、溶融した樹脂に色々な発泡剤を圧
入し、色々な押出条件の下で押出発泡を行ない、得られ
た発泡体の性質を検討した。Among the above-mentioned problems, the present inventor considered that it is suitable to use a polylactic acid resin in order to obtain a structural material having good abandonment and degradability. Therefore, using various grades of polylactic acid-based resin, this was put into an extruder and melted, various foaming agents were pressed into the melted resin, and extrusion foaming was performed under various extrusion conditions to obtain The properties of the foam were investigated.

【００１１】その結果、ポリ乳酸系樹脂については、こ
れまではその中のＤ−体とＬ−体との組成に余り注意が
払われなかったが、この発明者は、ポリ乳酸系樹脂を構
成するＤ−体とＬ−体との共重合割合が、押出発泡によ
って得られる発泡体の性質に大きく影響することを見出
した。すなわち、押出発泡によって機械的強度の大きい
発泡体を得るには、ポリ乳酸系樹脂としてＤ−体とＬ−
体とが、そのうちの一方が２〜１０％で、他方が９８〜
９０％の割合に共重合しているものを選んで用いるの
が、必要であることを見出した。As a result, regarding polylactic acid-based resins, until now, little attention has been paid to the composition of the D-form and L-form therein, but the present inventor constructed the polylactic acid-based resin. It has been found that the copolymerization ratio of the D-form and the L-form to significantly influence the properties of the foam obtained by extrusion foaming. That is, in order to obtain a foam having high mechanical strength by extrusion foaming, the D-form and the L-form as the polylactic acid resin are used.
One of the body is 2-10%, the other is 98-
It has been found that it is necessary to select and use those copolymerized in a proportion of 90%.

【００１２】また、この発明者は、ポリ乳酸系樹脂は、
これを押出発泡させる際に、発泡倍率を上昇させようと
すると、得られた発泡体は連続気泡率が通常５０％以上
という程の、連続気泡率の高いものとなり、従って機械
的強度が低く、また断熱性の低いものとなることに気付
いた。そのために発泡倍率が高くて連続気泡率の低い発
泡体を得るには、押し出し操作に格別の工夫が必要であ
ることに気付いた。Further, the present inventor has found that the polylactic acid resin is
When it is attempted to increase the expansion ratio when it is extruded and foamed, the resulting foam has a high open cell rate, such that the open cell rate is usually 50% or more, and therefore the mechanical strength is low. I also noticed that the insulation is low. Therefore, we have found that a special technique is required for the extrusion operation in order to obtain a foam having a high expansion ratio and a low open cell ratio.

【００１３】この発明者は、さらに検討を進めた結果、
ポリ乳酸系樹脂では押し出す時の樹脂温度が重要である
ことを見出した。すなわち、スチレン系樹脂などを材料
とする在来の押出発泡では、樹脂の融点又は軟化点より
高い温度で押出機から押し出して来たが、ポリ乳酸系樹
脂では、押出機から押し出す時の樹脂温度を、樹脂の融
点又は軟化点より低い温度に冷却し、樹脂がまだ流動性
を持っている間に押し出すと、発泡が容易となり、押出
物を高い倍率に発泡させることができ、しかも連続気泡
率の低いものとなることを見出した。この発明は、この
ような知見に基づいて完成されたものである。As a result of further study, the inventor found that
It was found that the resin temperature at the time of extrusion is important for the polylactic acid resin. That is, in conventional extrusion foaming using a styrene resin or the like as a material, the resin was extruded from the extruder at a temperature higher than the melting point or softening point of the resin, but in the case of polylactic acid resin, the resin temperature at the time of extrusion from the extruder was used. Is cooled to a temperature lower than the melting point or softening point of the resin and extruded while the resin is still fluid, foaming is facilitated and the extrudate can be expanded to a high ratio, and the open cell ratio It was found to be low. The present invention has been completed based on such knowledge.

【００１４】こうして、この発明は、特定組成のポリ乳
酸系樹脂の発泡体であって、高倍率に発泡していなが
ら、しかも連続気泡率が小さいという特性を持った新規
な発泡体を提供するものである。また、この発明はその
新規な発泡体の製造方法を提供するものである。Thus, the present invention provides a novel foamed product of a polylactic acid resin having a specific composition, which is foamed at a high expansion ratio and has a small open cell ratio. Is. The present invention also provides a method for producing the novel foam.

【００１５】すなわち、この発明は、乳酸のＤ−体とＬ
−体とが、そのうちの一方が２〜１０％で他方が９８〜
９０％の割合に共重合して、１１０〜１７０℃の融点を
持つポリ乳酸系樹脂からなる発泡体であって、見掛け密
度が０．１２ｇ／ｃｍ3 以下であり、連続気泡率が２０
％以下であることを特徴とする、遺棄分解性の良好な軽
量構造材及び断熱材を提供するものである。That is, the present invention relates to the D-form of lactic acid and L-form.
-The body is 2-10% of one and 98- of the other
A foam made of polylactic acid-based resin having a melting point of 110 to 170 ° C. copolymerized in a proportion of 90%, an apparent density of 0.12 g / cm 3 or less, and an open cell ratio of 20.
% Or less, the present invention provides a lightweight structural material and a heat insulating material having good abandonment degradability.

【００１６】また、この発明は、乳酸のＤ−体とＬ−体
とが、そのうちの一方が２〜１０％で他方が９８〜９０
％の割合で共重合したものであって、１１０〜１７０℃
の融点を持つポリ乳酸系樹脂を押出機内で溶融し、これ
に発泡剤として上記融点より低い沸点を持った脂肪族エ
ーテルを樹脂に対して０．５重量％以上含ませ、得られ
た発泡剤含有の溶融樹脂を、樹脂の融点と融点より４０
℃だけ低い温度との間の温度で押出機から押し出して発
泡させることを特徴とする遺棄分解性の良好な軽量構造
材の製造方法を提供するものである。According to the present invention, one of the D-form and the L-form of lactic acid is 2 to 10% and the other is 98 to 90%.
% Copolymerized at 110 to 170 ° C.
A polylactic acid-based resin having a melting point of 10% by weight is melted in an extruder, and 0.5% by weight or more of an aliphatic ether having a boiling point lower than the above-mentioned melting point is added to the resin as a foaming agent. The molten resin containing the melting point of the resin and
Disclosed is a method for producing a lightweight structural material having good abandonable decomposability, which comprises extruding from an extruder and foaming at a temperature between 0 ° C and lower.

【００１７】一般にポリ乳酸系樹脂のうち、Ｄ−体又は
Ｌ−体が１００％近くを占めている樹脂は、結晶性のも
のであり、Ｄ−体及びＬ−体のうちの一方の含有量が増
すに従い、樹脂は次第に非晶化の傾向を示し、一方が１
２％を越えると、樹脂は非晶性のものとなる、と云われ
ている。また、結晶性のポリ乳酸系樹脂は一般に融点が
高く、通常１００℃以上の融点を示すが、非晶性のポリ
乳酸系樹脂は融点がなく、ガラス転移点も約５０℃と低
く、従って耐熱性に乏しい、と云われている。Generally, among polylactic acid-based resins, a resin in which D-form or L-form occupies nearly 100% is a crystalline resin, and one of the D-form and the L-form is contained. The resin gradually shows the tendency of becoming amorphous as
When it exceeds 2%, the resin is said to be amorphous. In addition, crystalline polylactic acid-based resins generally have a high melting point and usually have a melting point of 100 ° C. or higher, but amorphous polylactic acid-based resins have no melting point and have a low glass transition point of about 50 ° C. It is said to be poor in sex.

【００１８】しかし、Ｄ−体とＬ−体との比がどのよう
な割合で含まれているポリ乳酸系樹脂が、押出発泡を行
うのに適しているかは知られていない。この発明者は、
この点について検討した結果、Ｄ−体とＬ−体とは、そ
のうちの一方が２〜１０％で、他方が９８〜９０％の割
合で共重合しているポリ乳酸系樹脂が、押出発泡をする
のに適していることを見出した。そこでこの発明では、
押出発泡を行うには、Ｄ−体が２〜１０％で、Ｌ−体が
９８〜９０％のポリ乳酸系樹脂を用いるか、又はＬ−体
が２〜１０％で、Ｄ−体が９８〜９０％のポリ乳酸系樹
脂を用いることとしたのである。However, it is not known what ratio of the D-form to the L-form contained in the polylactic acid resin is suitable for extrusion foaming. This inventor
As a result of studying this point, one of the D-form and the L-form is 2 to 10%, and the other polylactic acid-based resin is copolymerized at a ratio of 98 to 90%. Found to be suitable to do. So in this invention,
In order to carry out extrusion foaming, a polylactic acid-based resin in which the D-form is 2 to 10% and the L-form is 98 to 90%, or the L-form is 2 to 10% and the D-form is 98%. It was decided to use up to 90% of polylactic acid based resin.

【００１９】上述のＤ−体とＬ−体との共重合割合は、
ポリ乳酸系樹脂の製造時における原料の仕込量から特定
することができるが、また得られたポリ乳酸系樹脂から
も測定することができる。それは、Ｄ−体又はＬ−体の
場合と同様に、比旋光度を測定することによって定める
ことができる。それは例えば、次のようにして測定する
ことができる。The copolymerization ratio of the above-mentioned D-form and L-form is
It can be specified from the charged amount of the raw material during the production of the polylactic acid resin, but it can also be measured from the obtained polylactic acid resin. It can be determined by measuring the specific rotation, as in the D- or L-form. It can be measured, for example, as follows.

【００２０】まず、問題のポリ乳酸系樹脂をクロロホル
ムに溶解し、濃度が１０ｍｇ／ｍｌのクロロホルム溶液
を調製する。旋光計（ＪＡＳＣＯ ＤＩＰ−１４０）を
使用して、２５℃で波長５８９ｍｍの偏光を照射して上
記溶液の比旋光度を測定する。また、比較のために、Ｄ
−体１００％（又はＬ−体１００％）からなるポリ乳酸
系樹脂について、上と同様にして比旋光度を測定しても
よいが、通常はこの比旋光度は、既に測定されていて、
＋又は−１５６度とされている。そこで、上記問題の樹
脂の比旋光度が１５６度からどの程度ズレているかを測
定し、そのズレの程度をもって（１）及び（２）式によ
りＤ−体又はＬ−体の含有量を決定する。 Ｄ−体割合（％）＝｛比旋光度−（−１５６）｝÷｛１５６−（−１５ ６）｝×１００ （１） Ｌ−体割合（％）＝１００−（Ｄ−体割合） （２）First, the polylactic acid resin in question is dissolved in chloroform to prepare a chloroform solution having a concentration of 10 mg / ml. Using a polarimeter (JASCO DIP-140), the specific rotation of the solution is measured by irradiating polarized light having a wavelength of 589 mm at 25 ° C. Also, for comparison, D
The specific optical rotation may be measured in the same manner as above for the polylactic acid-based resin consisting of 100% of the -body (or 100% of the L-body), but normally, this specific optical rotation has already been measured,
It is set to + or -156 degrees. Therefore, how much the specific rotation of the resin in question deviates from 156 degrees is measured, and the content of the D- form or L- form is determined by the expressions (1) and (2) based on the degree of the deviation. . D-body ratio (%) = {specific optical rotation-(-156)} ÷ {156-(− 156)} × 100 (1) L-body ratio (%) = 100- (D-body ratio) ( 2)

【００２１】この発明では、こうして決定された含有割
合を基準にして、Ｄ−体とＬ−体のうち、一方が２〜１
０％で、他方が９８〜９０％の割合で、共重合したポリ
乳酸系樹脂を選んで使用する。その理由は色々な組成の
ポリ乳酸系樹脂について押出発泡の実験を行って得られ
た結果に由来している。すなわち、Ｄ−体及びＬ−体の
共重合体の中で一方が２％より少ないと、ポリ乳酸系樹
脂は溶融状態から急激に結晶化するために、発泡に適し
た溶融粘度を樹脂に保持させることが困難となるからで
ある。また、逆に１０％より多くなると、樹脂は非晶化
の傾向を示し、融点又は軟化点が低くなり、実用に適し
たものとならないからである。In the present invention, one of the D-form and the L-form is 2-1 based on the content ratio thus determined.
The copolymerized polylactic acid-based resin is selected and used in an amount of 0% and the other 98-90%. The reason is derived from the results obtained by conducting the experiment of extrusion foaming for polylactic acid resins having various compositions. That is, when one of the D- and L-copolymers is less than 2%, the polylactic acid-based resin is rapidly crystallized from the molten state, so that the resin has a melt viscosity suitable for foaming. This is because it will be difficult to do. On the other hand, if it is more than 10%, the resin tends to be non-crystallized and the melting point or softening point becomes low, so that it is not suitable for practical use.

【００２２】この発明では、ポリ乳酸系樹脂として、上
記の共重合割合を持つと同時に、１１０〜１７０℃の融
点を持つものを選んで用いる。ポリ乳酸系樹脂の中には
融点が１７０℃以上のもの、例えば融点が１８０℃のも
のもあるが、融点が１７０℃以上のものは、結晶性に富
むために、上述のように発泡に適した粘度を示さないこ
とが多いので、これを避けることとした。融点は、ＪＩ
Ｓ Ｋ ７１２１に定める方法によって測定した値を用
いる。１１０〜１７０℃の融点範囲内では、１２０〜１
６０℃の範囲内のものが好ましく、さらには１２５〜１
５５℃の範囲内のものが最も好ましい。In the present invention, as the polylactic acid resin, a resin having the above-mentioned copolymerization ratio and a melting point of 110 to 170 ° C. is selected and used. Some polylactic acid-based resins have a melting point of 170 ° C. or higher, for example, a melting point of 180 ° C., but those having a melting point of 170 ° C. or higher are suitable for foaming as described above because of their rich crystallinity. Since it often does not show viscosity, it was decided to avoid this. Melting point is JI
The value measured by the method defined in SK 7121 is used. Within the melting point range of 110 to 170 ° C., 120 to 1
It is preferably in the range of 60 ° C, and more preferably 125 to 1
Most preferred is within the range of 55 ° C.

【００２３】共重合割合と融点とが上述の範囲内にある
ポリ乳酸系樹脂の中でも、とくにメルトマスフローレー
トが１〜１５ｇ／１０分のポリ乳酸系樹脂を用いること
が好ましい。その中では、５〜１０ｇ／１０分のメルト
マスフローレートを示すものを用いることがとくに好ま
しい。この場合、メルトマスフローレートは、ＪＩＳＫ
７２１０が規定する方法に従い、１９０℃で２．１６
ｋｇの荷重をかけて測定した値である。Among the polylactic acid resins having the copolymerization ratio and the melting point within the above ranges, it is particularly preferable to use the polylactic acid resin having a melt mass flow rate of 1 to 15 g / 10 min. Among them, it is particularly preferable to use one having a melt mass flow rate of 5 to 10 g / 10 minutes. In this case, the melt mass flow rate is JISK
2.16 at 190 ° C according to the method specified by 7210
It is a value measured by applying a load of kg.

【００２４】この発明では、押出機として色々な形式の
ものを用いることができる。例えば、単軸押出機でも、
二軸押出機でも、またこれらを連結したタンデム押出機
でも用いることができる。押出機としては、ポリ乳酸系
樹脂を溶融し、よく混練できるとともに、これに発泡剤
を均一に含ませることができて、そのあとで引き続き樹
脂を或る温度まで冷却して、押し出すことができるもの
を用いることが好ましい。In the present invention, various types of extruders can be used as the extruder. For example, even with a single screw extruder,
A twin-screw extruder or a tandem extruder in which these are connected can be used. As an extruder, a polylactic acid-based resin can be melted and kneaded well, and a foaming agent can be uniformly contained in this, and then the resin can be cooled to a certain temperature and extruded. It is preferable to use one.

【００２５】この発明では、押出機内で溶融されたポリ
乳酸系樹脂に発泡剤を含ませる。発泡剤としては、エー
テル類、とくにジメチルエーテルを用いることが最も好
ましいが、その理由は次のとおりである。すなわち、エ
ーテル類とくにジメチルエーテルは、ポリ乳酸系樹脂と
の相溶性に富み、また蒸発の潜熱が大きいために、押し
出された樹脂を短時間のうちに一様に冷却することがで
き、従って高い倍率に一様に樹脂を発泡させることがで
きるからである。また、ハロゲン化炭化水素に比べ、環
境に優しいからである。この場合、ジメチルエーテルの
使用量は、樹脂に対して０．５〜２５％というような、
広い範囲で変化させることができる。そのうちでは、
１．０〜２２％が好ましく、１．５〜１９％が最も好ま
しい。In the present invention, the polylactic acid resin melted in the extruder contains a foaming agent. As the foaming agent, it is most preferable to use ethers, particularly dimethyl ether, for the following reason. That is, ethers, especially dimethyl ether, are highly compatible with polylactic acid-based resins and have a large latent heat of vaporization, so that the extruded resin can be uniformly cooled in a short time, and therefore a high magnification ratio can be obtained. This is because the resin can be uniformly foamed. Also, it is more environmentally friendly than halogenated hydrocarbons. In this case, the amount of dimethyl ether used is 0.5 to 25% with respect to the resin,
It can be varied over a wide range. Of which,
1.0-22% is preferable and 1.5-19% is the most preferable.

【００２６】但し、発泡性及び連続気泡率に悪影響を与
えない範囲で他の発泡剤、例えばプロパン、ｎ−ブタ
ン、ｉ−ブタン、ｎ−ペンタン、ｉ−ペンタン、ヘキサ
ンのような脂肪族炭化水素類、ベンゼン、トルエンのよ
うな芳香族炭化水素類、アゾジカーボンアミド、ヘキサ
メチレンテトラミンのような分解されて気体を発生する
固体化合物、空気、窒素、二酸化炭素等を併用して使用
してもよい。However, other foaming agents such as propane, n-butane, i-butane, n-pentane, i-pentane and hexane are used as long as they do not adversely affect the foamability and open cell ratio. , Benzene, aromatic hydrocarbons such as toluene, azodicarbonamide, solid compounds such as hexamethylenetetramine that decompose to generate gas, air, nitrogen, carbon dioxide, etc. Good.

【００２７】この発明では、押出機内でポリ乳酸系樹脂
に上述の発泡剤を均一に混合する。このためには樹脂を
溶融し、これに発泡剤を圧入してよく混練することが必
要である。良く混合するには混合能力の大きいスクリュ
ー、例えば多数のピンを備えたスクリューを用いたり、
スクリューフライトに多数の切り込みを設けたスクリュ
ーを用いて溶融樹脂と発泡剤とをよく混合する。発泡剤
が圧入される時の樹脂は、当然樹脂の融点より高い温度
にあり、通常は３０〜７０℃だけ高い温度になってい
る。In the present invention, the above-mentioned foaming agent is uniformly mixed with the polylactic acid resin in the extruder. For this purpose, it is necessary to melt the resin, press-fit the foaming agent into the resin, and knead well. To mix well, use a screw with a large mixing capacity, such as a screw with many pins,
The molten resin and the foaming agent are mixed well using a screw provided with a large number of cuts in the screw flight. The resin when the foaming agent is press-fitted is naturally at a temperature higher than the melting point of the resin, and is usually 30 to 70 ° C. higher.

【００２８】この発明では、上述の発泡剤を含んだポリ
乳酸系樹脂を引き続き冷却する。この冷却には色々な方
法を採ることができる。例えば押出機のバレルを空気或
いは冷却水で冷却する。発泡剤を含んだポリ乳酸系樹脂
は押出機のバレルから冷却されつつ、押出機のスクリュ
ーにより十分に混練される。こうして発泡剤含有樹脂を
一様に樹脂の融点以下に冷却する。発泡剤含有樹脂は前
述したように、樹脂の融点とその融点より約４０℃だけ
低い温度とするが、更には樹脂の融点より約３５℃だけ
低い温度からその融点より約１０℃だけ低い温度が好ま
しく、特には樹脂の融点より約３０℃だけ低い温度から
その融点より約２０℃だけ低い温度との間とすることが
好ましい。In the present invention, the polylactic acid resin containing the above-mentioned foaming agent is subsequently cooled. Various methods can be adopted for this cooling. For example, the barrel of the extruder is cooled with air or cooling water. The polylactic acid-based resin containing the foaming agent is sufficiently kneaded by the screw of the extruder while being cooled from the barrel of the extruder. In this way, the foaming agent-containing resin is uniformly cooled below the melting point of the resin. As described above, the blowing agent-containing resin has a melting point of the resin and a temperature lower than the melting point by about 40 ° C., and further, a temperature lower than the melting point of the resin by about 35 ° C. to a temperature lower than the melting point by about 10 ° C. It is particularly preferred to be between about 30 ° C. below the melting point of the resin and about 20 ° C. below its melting point.

【００２９】押出機中で溶融状態にある発泡剤含有のポ
リ乳酸系樹脂は、押出機内で冷却され始めて暫らくの間
は融点以下に冷却されても、なお暫らくは流動性を持っ
ている。このために、融点よりも数拾度低い温度にし
て、押出機から押し出すことができる。すなわち、押出
機の直後（タンデム型押出機の場合は最後段の押出機の
直後）に付設されたブレーカープレートの位置で、樹脂
の温度を測定すると、発泡剤含有樹脂の温度が、樹脂の
融点と融点より４０℃だけ低い温度との間にある間は、
樹脂が云わば過冷却された状態にあって、なお流動性を
持っているため、押出機から押し出すことができる。The foaming agent-containing polylactic acid-based resin in a molten state in the extruder has fluidity even if it is cooled to a temperature below its melting point for a while after starting to be cooled in the extruder. . For this reason, it is possible to extrude from the extruder at a temperature several degrees lower than the melting point. That is, when the temperature of the resin is measured at the position of the breaker plate attached immediately after the extruder (immediately after the last-stage extruder in the case of a tandem type extruder), the temperature of the foaming agent-containing resin is the melting point of the resin. Between 40 ° C and 40 ° C below the melting point,
The resin can be extruded from the extruder because it is in a supercooled state, so to speak, and still has fluidity.

【００３０】そこで、この発明では、発泡剤含有のポリ
乳酸系樹脂が、樹脂の融点と融点より４０℃だけ低い温
度との間にある間に、樹脂を押出機から押し出すことと
する。それは、この状態にあるとき、発泡剤含有のポリ
乳酸系樹脂が発泡するに適した溶融粘度を示すからであ
る。このような状態で押し出すことは、この発明におけ
る大きな特徴である。その理由は次のとおりである。Therefore, in the present invention, the resin is extruded from the extruder while the polylactic acid resin containing the foaming agent is between the melting point of the resin and the temperature 40 ° C. lower than the melting point. This is because, in this state, the polylactic acid resin containing the foaming agent exhibits a melt viscosity suitable for foaming. Extruding in such a state is a great feature of the present invention. The reason is as follows.

【００３１】一般に熱可塑性合成樹脂を押出発泡させる
場合には、結晶性の樹脂では結晶融点以上の温度で押し
出し、非晶性の樹脂ではガラス転移点以上の温度で押し
出すのが普通である。なぜならば融点以下の温度やガラ
ス転移点以下の温度で押し出そうとすると、樹脂が金型
の中で固化して押し出すことができなくなるからであ
る。In general, when a thermoplastic synthetic resin is extruded and foamed, a crystalline resin is usually extruded at a temperature equal to or higher than a crystal melting point, and an amorphous resin is extruded at a temperature equal to or higher than a glass transition point. This is because if the resin is extruded at a temperature below the melting point or below the glass transition point, the resin will solidify in the mold and cannot be extruded.

【００３２】事実これまでは、例えば樹脂として融点が
２５５℃の結晶性のポリエチレンテレフタレートを用い
て、これを押出発泡させるには、樹脂の温度を２７０〜
２９０℃として押し出して来たし、また樹脂として融点
が１６０℃のポリプロピレンを押出発泡させるには、樹
脂の温度を１６５〜１７５℃として押し出して来た。ま
た、樹脂としてガラス転移点が９０〜９５℃の非晶性の
ポリスチレンを押出発泡させるには、樹脂の温度を１２
０〜１６０℃として押し出して来た。何れも押出時の樹
脂の温度は、樹脂の融点又はガラス転移点よりも高い温
度とされて来た。ところが、この発明では、上述のよう
に樹脂の融点又はガラス転移点よりも低い温度で押し出
すので、この点で従来の技術と大きく異なり、この発明
の特徴事項が構成されている。In fact, in the past, for example, crystalline polyethylene terephthalate having a melting point of 255 ° C. was used as a resin, and the resin was heated at a temperature of 270 to 270 for extrusion foaming.
It was extruded at 290 ° C., and in order to extrude and foam polypropylene having a melting point of 160 ° C. as a resin, the resin was extruded at a temperature of 165 to 175 ° C. Further, in order to extrude and foam amorphous polystyrene having a glass transition point of 90 to 95 ° C. as a resin, the temperature of the resin should be 12
It extruded as 0-160 ℃. In both cases, the temperature of the resin during extrusion has been set to a temperature higher than the melting point or glass transition point of the resin. However, in the present invention, since the resin is extruded at a temperature lower than the melting point or the glass transition point of the resin as described above, this point is largely different from the conventional technique, and the characteristic feature of the present invention is constituted.

【００３３】この発明では、押出機からポリ乳酸系樹脂
を押し出すに際し、押出機の先端に付設した金型に樹脂
を通して押し出す。このとき樹脂は、融点と融点より４
０℃だけ低い温度との間の温度になっていて、押し出し
を行うに充分な流動性を持っており、また発泡を行うに
適した溶融粘度を持っている。In the present invention, when the polylactic acid resin is extruded from the extruder, the resin is extruded through a die attached to the tip of the extruder. At this time, the resin has a melting point and
It has a temperature between 0 ° C. and a low temperature, has sufficient fluidity for extrusion, and has a melt viscosity suitable for foaming.

【００３４】金型としては、得ようとする発泡体の断面
形状のオリフィスを持ったものを用いる。金型のオリフ
ィスから押し出されたあとの樹脂は、従来の押出発泡の
操作と全く同様に、外形を整えられるとともに空気或い
は水で直接又は間接的に冷却されて発泡体となる。As the mold, one having an orifice having a cross-sectional shape of the foam to be obtained is used. After being extruded from the orifice of the mold, the resin is trimmed and cooled directly or indirectly with air or water to form a foam, just like the conventional extrusion foaming operation.

【００３５】また、断面積の大きい板状発泡体をつくる
場合、発泡剤としてジメチルエーテルを使用し、樹脂温
度を十分に下げただけでは、高倍率に発泡し、連続気泡
率が低く、熱伝導率が低い発泡体をつくることは難し
い。Further, when a plate-like foam having a large cross-sectional area is produced, dimethyl ether is used as a foaming agent, and the resin temperature is sufficiently lowered to foam at a high magnification, the open cell ratio is low, and the thermal conductivity is low. It is difficult to make low foams.

【００３６】板状発泡体を製造する際には溶融樹脂と発
泡剤とを良く混合・混練した上で、発泡剤を含有した溶
融樹脂の温度を均一にして、金型に該溶融樹脂を送り込
まないと、溶融樹脂中に発泡剤が不均一に分散し、発泡
体の厚みや幅方向で品質のバラツキ、具体的には連続気
泡率、発泡倍率や強度のバラツキが大きく、粗悪な板状
発泡体となってしまう。樹脂温度の均一性についてはブ
レーカープレートの２点（ブレーカープレートの樹脂通
過断面の中心部と樹脂通過断面の中心部と樹脂通過最外
部との中間点）で樹脂温度を測定することにより管理す
ることができる。その際、上述の２点で測定した温度差
は５℃、更には３℃、特には２℃以下とすることが好ま
しい。樹脂温度のバラツキを少なくする方法としてはい
くつか挙げることができる。When producing a plate-like foam, the molten resin and the foaming agent are thoroughly mixed and kneaded, and then the temperature of the molten resin containing the foaming agent is made uniform, and the molten resin is fed into the mold. If not, the foaming agent will be unevenly dispersed in the molten resin, and the quality of the foam will vary in the thickness and width directions, specifically, there will be large variations in the open cell ratio, expansion ratio and strength, and poor plate-like foaming. It becomes a body. The uniformity of the resin temperature should be controlled by measuring the resin temperature at two points on the breaker plate (the center of the resin passage cross section of the breaker plate and the center of the resin passage cross section and the outermost portion of the resin passage). You can At that time, the temperature difference measured at the above-mentioned two points is preferably 5 ° C., more preferably 3 ° C., and particularly preferably 2 ° C. or less. There are several methods for reducing the variation in resin temperature.

【００３７】押出前のポリ乳酸系樹脂の結晶化度は少
なくとも２０％以上とする。ポリ乳酸系樹脂の結晶化度
が低いと、押出機のホッパー下付近でポリ乳酸系樹脂の
ブロッキングが生じる。このブロッキングが押出量変動
を引き起こし、樹脂温度のバラツキを生じさせる。The crystallinity of the polylactic acid resin before extrusion is at least 20% or more. When the crystallinity of the polylactic acid resin is low, the polylactic acid resin is blocked near the hopper of the extruder. This blocking causes fluctuations in the extrusion rate, causing variations in the resin temperature.

【００３８】適正な温度範囲になるまで押出量を下
げ、押出機内で溶融樹脂の滞留時間を長くし、樹脂温度
の均一化を図る。タンデム式押出機を使用する場合の二
段目押出機の好ましい溶融樹脂の平均滞留時間は５〜１
５分間、更には６〜１３分間、特には８〜１１分間であ
る。但し、滞留時間が長すぎると、溶融樹脂が押出機内
で固化するため好ましくない。The amount of extrusion is lowered until the temperature is within an appropriate range, the residence time of the molten resin is lengthened in the extruder, and the resin temperature is made uniform. When using a tandem extruder, the average residence time of the molten resin in the second-stage extruder is preferably 5 to 1
5 minutes, more preferably 6 to 13 minutes, especially 8 to 11 minutes. However, if the residence time is too long, the molten resin solidifies in the extruder, which is not preferable.

【００３９】適正なスクリュー回転数と押出量で押し
出し、過度の剪断発熱を防ぐ。タンデム式押出機を使用
する場合の２段目押出機の口径と押出量とスクリュー回
転数の関係は下記の式の範囲内とすることが好ましい。 １＜押出機口径の二乗×スクリュー回転数／押出量＜２ （押出機口径：ｍｍ、スクリュー回転数：ｒｐｍ、押出
量ｇ／ｈｒ）Extrusion is carried out at an appropriate screw rotation speed and extrusion rate to prevent excessive shear heat generation. When the tandem type extruder is used, the relationship between the diameter of the second stage extruder, the amount of extrusion and the screw rotation speed is preferably within the range of the following formula. 1 <Square of extruder diameter x screw rotation speed / extrusion amount <2 (extruder diameter: mm, screw rotation speed: rpm, extrusion amount g / hr)

【００４０】混合・混練性に優れたスクリューを使用
する。タンデム式押出機を使用する場合、二段目押出機
のスクリューはその長さの３０％以上の部分においてピ
ンや切り込み部分を有するものを使用する。特に発熱が
生じにくく、混合・混練効果に優れた切り込み部分をス
クリューの長さの４０％以上有するスクリューを使用す
ることがより好ましい。A screw having excellent mixing / kneading properties is used. When a tandem type extruder is used, the screw of the second stage extruder has a pin or a cut portion at a portion of 30% or more of its length. In particular, it is more preferable to use a screw having a cut portion having 40% or more of the length of the screw, which is excellent in the effect of mixing and kneading and which hardly generates heat.

【００４１】この発明では、押出機からポリ乳酸系樹脂
を押し出すに際し、押出機の先端に付設した金型に樹脂
を通して押し出す。このとき樹脂は、発泡に適した温度
でかつ樹脂温度のバラツキが少ない状態になっていて、
押し出しを行うに充分な流動性を持っており、また発泡
を行うに適した溶融粘度を持っている。In the present invention, when the polylactic acid resin is extruded from the extruder, the resin is extruded through a die attached to the tip of the extruder. At this time, the resin has a temperature suitable for foaming and is in a state where there is little variation in the resin temperature,
It has sufficient fluidity for extrusion and has a melt viscosity suitable for foaming.

【００４２】金型としては、得ようとする発泡体の断面
形状のオリフィスから押し出された後の樹脂は、従来の
押出発泡の操作と全く同様に、外形を整えられるととも
に空気あるいは水で直接的にあるいは間接的に冷却され
て発泡体となるが、効率よく板状発泡体を製造するため
には口金部が平行溝であるフラット金型を使用すること
が好ましい。フラット金型の口金間隙は得ようとする発
泡体の厚みにもよるが、大体０．７〜２ｍｍ、好ましく
は０．９〜１．５ｍｍの間隙が好ましい。また口金の内
面はできる限り溶融樹脂との剪断発熱が抑えられるよ
う、一部或いは全部がポリ四弗化エチレン樹脂からなる
コーティング材で樹脂の通過面をコーティングすること
が好ましい。発泡剤を含んだ溶融樹脂は通常発泡シート
やロッド状発泡体をつくる場合よりも低い剪断速度で押
し出す。ポリ乳酸系樹脂の板状発泡体を押し出す際の好
ましい剪断速度［剪断速度＝６×押出量／（口金幅×口
金間隙の二乗）、ポリ乳酸系樹脂の樹脂密度は１．１ｇ
／ｃｍ3 とする］は１５０〜９００ｓｅｃ- 1 、更には
２００〜８００ｓｅｃ- 1 、特には２５０〜７００ｓｅ
ｃ- 1 である。As the mold, the resin after being extruded from the orifice of the cross-sectional shape of the foam to be obtained has its outer shape regulated and can be directly treated with air or water just as in the conventional extrusion foaming operation. Although it is cooled indirectly or indirectly to form a foam, it is preferable to use a flat mold having parallel grooves in the die for efficiently manufacturing a plate-shaped foam. The die gap of the flat die depends on the thickness of the foam to be obtained, but a gap of about 0.7 to 2 mm, preferably 0.9 to 1.5 mm is preferable. Further, it is preferable that the inner surface of the die is coated with a coating material, which is partially or entirely made of polytetrafluoroethylene resin, so as to suppress heat generation by shearing with the molten resin as much as possible. The molten resin containing the foaming agent is usually extruded at a lower shear rate than when a foamed sheet or a rod-shaped foam is produced. Preferred shear rate for extruding a plate-like foam of polylactic acid resin [shear rate = 6 x extrusion amount / (base width x base gap of square), and resin density of polylactic acid resin is 1.1 g.
/ A cm 3] is 150~900sec - 1, further 200~800sec - 1, especially 250~700se
c - 1 .

【００４３】金型から押し出された発泡剤含有溶融樹脂
は、口金の先端に密接に取り付けられた、２枚の板を向
きあわせてなる成形装置を通過させ、成形と同時に冷却
することにより成形する。ポリ乳酸系樹脂のガラス転移
温度は大体６０℃であることから、２枚の板を向きあわ
せてなる成形装置通過直後の板状発泡体の表面温度は６
０℃以下、発泡体内部の温度を考慮すると５０℃以下、
特には４０℃以下となるように成形装置で冷却する。発
泡体の表面温度が６０℃より高いと、発泡体の反りや曲
がりが発生しやすく好ましくない。ポリ乳酸系樹脂のガ
ラス転移温度はポリスチレン系樹脂のガラス転移温度に
比べ３０〜４０℃低いことから、成形装置においてポリ
スチレン系樹脂の板状発泡体を製造する場合より多くの
熱量を発泡体から奪熱する必要がある。その方法として
は例えば、成形装置の２枚の板の内部に３０℃以下、好
ましくは２５℃以下の冷却水を通水し、２枚の板の表面
温度を下げるとともに、２枚の板の長さを通常のポリス
チレン系樹脂の板状発泡体をつくる際に使用する場合よ
りも長くする。或いは押出量を下げて、板状発泡体が成
形装置を通過する時間を長くすることで、板状発泡体か
らの脱熱量を大きくする。或いは、２対の２枚の板から
なる成形部分からなる成形装置を使用する方法などがあ
る。The foaming agent-containing molten resin extruded from the mold is molded by passing through a molding device, which is closely attached to the tip of the die and made by facing two plates, and is cooled at the same time as the molding. . Since the glass transition temperature of the polylactic acid resin is about 60 ° C., the surface temperature of the plate-like foam immediately after passing through the molding apparatus, which is formed by facing two plates, is 6
0 ℃ or less, 50 ℃ or less considering the temperature inside the foam,
Particularly, it is cooled by a molding apparatus so that the temperature becomes 40 ° C. or lower. If the surface temperature of the foam is higher than 60 ° C, the foam may be warped or bent, which is not preferable. Since the glass transition temperature of the polylactic acid resin is lower than that of the polystyrene resin by 30 to 40 ° C., a larger amount of heat is taken from the foam than in the case of manufacturing the plate foam of the polystyrene resin in the molding apparatus. Need to heat up. As a method thereof, for example, cooling water of 30 ° C. or lower, preferably 25 ° C. or lower is passed through the inside of the two plates of the molding apparatus to lower the surface temperature of the two plates and increase the length of the two plates. The length is made longer than that used when forming a plate-like foam of a usual polystyrene resin. Alternatively, the amount of heat removed from the plate-shaped foam is increased by lowering the extrusion amount and prolonging the time for the plate-shaped foam to pass through the molding device. Alternatively, there is a method of using a molding device composed of a molding portion composed of two pairs of two plates.

【００４４】本発明の板状発泡体が優れた断熱性能を発
揮し断熱材として好適に使用するためには、その厚みは
３ｍｍ以上、更には１０ｍｍ以上、特には２０ｍｍ以上
とすることが好ましい。In order for the plate-shaped foam of the present invention to exhibit excellent heat insulating performance and be suitably used as a heat insulating material, its thickness is preferably 3 mm or more, more preferably 10 mm or more, and particularly preferably 20 mm or more.

【００４５】こうして樹脂を少なくとも１０倍以上に発
泡させることができる。従って得られた発泡体は、見掛
け密度が０．１２ｇ／ｃｍ3 以下の均一微細に発泡した
ものとなっている。しかも、この発泡体はこのように高
い倍率に発泡しており乍ら、独立気泡性のものであって
連続気泡が少なく、従って連続気泡率が２０％以下とな
っている。また、特に注意することにより連続気泡率を
１０％以下、さらには５％以下にすることもできる。Thus, the resin can be foamed at least 10 times or more. Therefore, the obtained foam is uniformly finely foamed with an apparent density of 0.12 g / cm 3 or less. Moreover, since this foam is foamed at such a high magnification, it is a closed-cell type and has few open cells, and therefore the open cell rate is 20% or less. Also, with particular attention, the open cell rate can be set to 10% or less, and further to 5% or less.

【００４６】このように連続気泡率が２０％以下の低い
ものとなっているため、この発泡体は機械的強度にすぐ
れ、また熱絶縁にすぐれたものとなっている。得られた
発泡体の機械的強度について云えば、５％圧縮強度が
０．０８〜１．２ＭＰａ、さらには０．０９〜１．１Ｍ
Ｐａであり、圧縮弾性率が１．８〜３０ＭＰａ、さらに
は２．０〜２５ＭＰａであり、曲げ強度が０．５〜３．
２ＭＰａ、さらには０．６〜３．０ＭＰａであり、曲げ
弾性率が０．６〜３０ＭＰａ、さらには０．７〜２８Ｍ
Ｐａである。また、熱絶縁性について云えば、得られた
発泡体の熱伝導率が０．０４０Ｗ／ｍｋ以下であって、
ＪＩＳ Ａ９５１１に規定されているポリスチレン系樹
脂発泡体の熱伝導率に匹敵する値となっている。Since the open cell ratio is as low as 20% or less, the foam has excellent mechanical strength and thermal insulation. Regarding the mechanical strength of the obtained foam, the 5% compressive strength is 0.08 to 1.2 MPa, and further 0.09 to 1.1 M.
Pa, the compression elastic modulus is 1.8 to 30 MPa, further 2.0 to 25 MPa, and the bending strength is 0.5 to 3.
2 MPa, further 0.6 to 3.0 MPa, flexural modulus 0.6 to 30 MPa, further 0.7 to 28 M
Pa. In terms of thermal insulation, the obtained foam has a thermal conductivity of 0.040 W / mk or less,
The value is comparable to the thermal conductivity of the polystyrene resin foam specified in JIS A9511.

【００４７】この発明で得られたポリ乳酸系樹脂発泡体
は、上述のような性質を持っているから、これまでポリ
スチレン系樹脂発泡体が用いられていた分野で広く用い
ることができる。すなわち、軽量構造材としては、包装
材、緩衝材、建築土木材、食品用容器、工業用部材等と
して使用することができる。Since the polylactic acid resin foam obtained by the present invention has the above-mentioned properties, it can be widely used in the fields where polystyrene resin foams have been used so far. That is, as a lightweight structural material, it can be used as a packaging material, a cushioning material, a building earth and timber, a food container, an industrial member, and the like.

【００４８】断熱材としては、建築土木用断熱材（屋根
用断熱材、屋上用断熱材、壁断熱材、床断熱材、水道・
温水配管用保温材、バス用保温材、シンク用防露材
等）、自動車用部材（天井材、インパネ材、ドア材
等）、パイプカバー及びタンク類用断熱材、ボンベ用断
熱材、食品用断熱材等（生鮮食品トレー、弁当箱、保温
カップ及びトレー、インスタント食品容器、飲料カッ
プ、魚箱、保冷容器）として使用することができる。特
に環境に優しい発泡剤を使用して低い熱伝導率を達成し
ているので、建築土木用断熱材として好適に使用でき
る。As the heat insulating material, a heat insulating material for building civil engineering (a heat insulating material for a roof, a heat insulating material for a roof, a wall heat insulating material, a floor heat insulating material, a water supply,
Heat insulation material for hot water pipes, heat insulation material for baths, dew-proof materials for sinks, etc.), automotive parts (ceiling materials, instrument panel materials, door materials, etc.), heat insulation materials for pipe covers and tanks, heat insulation materials for cylinders, food products It can be used as a heat insulating material (fresh food tray, lunch box, heat retaining cup and tray, instant food container, beverage cup, fish box, cold container). Since a low thermal conductivity is achieved by using an environment-friendly foaming agent, it can be suitably used as a heat insulating material for building civil engineering.

【００４９】しかも、この発泡体は、ポリ乳酸系樹脂で
作られているから、日光風雨に直接長期にわたって曝さ
れない限り、すぐに劣化することがない。しかし、廃品
となったあとで遺棄され、とくに日光風雨に長期間曝さ
れたり、地中に埋没されたりすると次第に分解し、炭酸
ガスと水のような無害なものとなる。従って、この発泡
体は遺棄分解性の良好な軽量構造材として有用なもので
ある。この発明は、このような利益を与えるものであ
る。Moreover, since this foam is made of polylactic acid resin, it does not deteriorate immediately unless it is directly exposed to sunlight, wind and rain for a long period of time. However, after being discarded, it is abandoned, and when it is exposed to sunlight and rain for a long time or buried in the ground, it gradually decomposes and becomes harmless like carbon dioxide and water. Therefore, this foam is useful as a lightweight structural material having good abandonment and degradability. The present invention provides such benefits.

【００５０】なお、この発明では、従来技術で行われて
来たように、ポリ乳酸系樹脂に種々の添加剤を加えて、
得られる発泡体の性質に変化を与えることができる。例
えば、タルク、炭酸カルシウム、弗素樹脂粉末等の気泡
調整剤を加えて、発生する気泡を調整することができ
る。そのほか、難燃剤、帯電防止剤、着色剤などを加え
ることができる。In the present invention, various additives have been added to the polylactic acid resin, as has been done in the prior art.
Changes can be made in the properties of the resulting foam. For example, the bubbles generated can be adjusted by adding a bubble adjusting agent such as talc, calcium carbonate, or fluororesin powder. In addition, flame retardants, antistatic agents, coloring agents and the like can be added.

【００５１】[0051]

【発明の効果】この発明によれば、ポリ乳酸系樹脂とし
て、乳酸のＤ−体とＬ−体とが、そのうちの一方が２〜
１０％で他方が９８〜９０％の割合で共重合したものを
用いるので、押出機内で溶融したとき、樹脂が発泡に適
した溶融粘度を示すこととなる。また、発泡剤含有の溶
融樹脂を、樹脂の融点と融点より４０℃だけ低い温度と
の間の温度で押し出すこととしたので、樹脂は押出時に
発泡に適した溶融粘度を持って押し出される。このため
に、この発明方法によれば、所望通りに高い倍率で均一
に発泡した発泡体を得ることができる。しかも、ポリ乳
酸系樹脂として１１０〜１７０℃の融点を持つものを用
いたので、得られた発泡体は実用に適したものとなって
いる。According to the present invention, as the polylactic acid resin, one of D-form and L-form of lactic acid, one of which is 2 to
Since the copolymer of 10% and the other 98 to 90% is used, the resin exhibits a melt viscosity suitable for foaming when melted in the extruder. Further, since the molten resin containing the foaming agent is extruded at a temperature between the melting point of the resin and a temperature lower than the melting point by 40 ° C., the resin is extruded with a melt viscosity suitable for foaming during extrusion. Therefore, according to the method of the present invention, it is possible to obtain a foam that is uniformly foamed at a high magnification as desired. Moreover, since the polylactic acid resin having a melting point of 110 to 170 ° C. was used, the obtained foam is suitable for practical use.

【００５２】さらに、この発明では、押出機を用いて押
出発泡によることとしたので、連続して能率よく発泡体
を得ることができる。また、この発明では増粘剤を用い
ないので、ポリ乳酸系樹脂は遺棄分解性をそのまま保持
するので、環境に優しい発泡体として種々の用途に向け
ることができる。Further, in the present invention, since the extrusion foaming is performed using the extruder, the foam can be continuously and efficiently obtained. Further, since a thickener is not used in the present invention, the polylactic acid-based resin retains its abandonable degradability as it is, and thus can be applied to various uses as an environmentally friendly foam.

【００５３】なお、この発明方法によれば、得られた発
泡体は微細な気泡を持ち均一に発泡したものとなる。ま
た、気泡調整剤の添加や発泡条件の調整により、得られ
る発泡体の密度を０．１２ｇ／ｃｍ3 以下、とりわけ
０．０１２ｇ／ｃｍ3 以上の範囲内で所望通りに調整す
ることができる。しかも、発泡体は上述のように連続気
泡率が２０％以下の低いものとなるので、機械的強度や
断熱性のすぐれたものであり、従って構造材として広く
使用することができる。また、この発明によれば厚みが
３ｍｍ以上で幅が１５０ｍｍ以上の発泡板を容易に作る
ことができる。この発明はこのような利益を与えるもの
である。According to the method of the present invention, the foam obtained has fine bubbles and is uniformly foamed. Further, the density of the resulting foam can be adjusted as desired within a range of 0.12 g / cm 3 or less, and particularly 0.012 g / cm 3 or more by adding a cell regulator and adjusting the foaming conditions. In addition, since the foam has a low open cell rate of 20% or less as described above, it has excellent mechanical strength and heat insulating properties, and thus can be widely used as a structural material. Further, according to the present invention, a foam plate having a thickness of 3 mm or more and a width of 150 mm or more can be easily manufactured. The present invention provides such benefits.

【００５４】[0054]

【発明の態様】以下に実施例と比較例とを挙げて、この
発明のすぐれている所以を具体的に明らかにする。以下
で、単に部と云うのは、重量部を表わしている。また、
押出機から発泡剤を含有した溶融樹脂を押し出す時の樹
脂の温度は、押出機先端と金型との間に、ブレーカープ
レートを付設し、このブレーカープレートの直後に図１
に示したようなブレーカープレートの中心部、及び中心
部と樹脂通路の最外部との中間点（以下、これをＤ／４
部という）に熱電対を固定して、この熱電対の示す温度
をもって示した。BEST MODE FOR CARRYING OUT THE INVENTION The advantages of the present invention will be specifically described below with reference to Examples and Comparative Examples. In the following, "parts" means "parts by weight". Also,
When the molten resin containing the foaming agent is extruded from the extruder, the temperature of the resin is determined by attaching a breaker plate between the tip of the extruder and the mold and immediately after the breaker plate.
The center part of the breaker plate as shown in Fig. 4 and the midpoint between the center part and the outermost part of the resin passage (hereinafter referred to as D / 4
The thermocouple is fixed to the part) and the temperature indicated by this thermocouple is shown.

【００５５】連続気泡率の測定 連続気泡率は、ＡＳＴＭ Ｄ−２８５６に準拠し、東京
サイエンス（株）製の空気比較式比重計１０００型を使
用し、１〜１／２〜１気圧方法で測定した。Measurement of open cell rate The open cell rate was measured by the method of 1-1 / 2 to 1 atm according to ASTM D-2856 using an air-comparison hydrometer 1000 manufactured by Tokyo Science Co., Ltd. did.

【００５６】見掛け密度の測定 日本工業規格 ＪＩＳ Ｋ ６７６７に所載の方法に準
拠して、次式により発泡体の見掛け密度（ｇ／ｃｍ3 ）
を求めた。（ここで、見掛け密度は見掛け全体密度のこ
とをいう） 見掛け密度＝［発泡体の重量（ｇ）］／［発泡体の嵩体
積（ｃｍ3 ）］Measurement of Apparent Density According to the method described in Japanese Industrial Standard JIS K 6767, the apparent density (g / cm 3 ) of the foam is calculated by the following formula.
I asked. (Here, apparent density refers to apparent overall density) Apparent density = [weight of foam (g)] / [bulk volume of foam (cm 3 )]

【００５７】熱伝導率の測定 熱伝導率は日本工業規格 ＪＩＳ Ａ １４１２（熱絶
縁材の熱伝導率及び熱抵抗の測定方法）に所載の方法に
準拠して測定した。ただし、平均温度（試験片温度）は
２０−２℃〜２０＋３℃とした。Measurement of Thermal Conductivity The thermal conductivity was measured according to the method described in Japanese Industrial Standard JIS A 1412 (Measurement method of thermal conductivity and thermal resistance of heat insulating material). However, the average temperature (test piece temperature) was set to 20-2 ° C to 20 + 3 ° C.

【００５８】５％圧縮強度及び圧縮弾性率 ５％圧縮強度及び圧縮弾性率はＪＩＳ Ａ９５１１（発
泡プラスチック保温材）に準拠して測定し、三方向（Ｍ
Ｄ，ＴＤ，ＶＤ）の平均値とした。 試験装置：テンシロン万能試験機 ＵＣＴ−１０Ｔ
（（株）オリエンテック） 試験片：２５（幅）×２５（長さ）×２５（厚み）（単
位はｍｍ） 試験速度：１０ｍｍ／ｍｉｎ 試験数：３5% compressive strength and compressive elastic modulus The 5% compressive strength and compressive elastic modulus were measured according to JIS A9511 (foamed plastic heat insulating material) and measured in three directions (M
The average value of (D, TD, VD). Testing equipment: Tensilon universal testing machine UCT-10T
(Orientec Co., Ltd.) Test piece: 25 (width) x 25 (length) x 25 (thickness) (unit: mm) Test speed: 10 mm / min Number of tests: 3

【００５９】曲げ強度及び曲げ弾性率 曲げ強度及び曲げ弾性率はＪＩＳ Ａ９５１１（発泡プ
ラスチック保温材）に準拠して測定し、二方向（ＭＤ、
ＴＤ）の平均値とした。 試験装置：テンシロン万能試験機 ＵＣＴ−１０Ｔ
（（株）オリエンテック） 試験片：５０（幅）×２００（長さ）×２０（厚み）
（単位はｍｍ） 支点間距離：１５０ｍｍ 試験速度：１０ｍｍ／ｍｉｎ 先端治具：加圧くさび・・・１０Ｒ 支持台・・・１
０Ｒ 試験数：３Bending Strength and Bending Elastic Modulus Bending strength and bending elastic modulus were measured in accordance with JIS A9511 (foamed plastic heat insulating material) and measured in two directions (MD,
The average value of TD) was used. Testing equipment: Tensilon universal testing machine UCT-10T
(Orientec Co., Ltd.) Test piece: 50 (width) x 200 (length) x 20 (thickness)
(Unit: mm) Distance between fulcrums: 150 mm Test speed: 10 mm / min Tip jig: pressure wedge ... 10R Support base ... 1
0R Number of tests: 3

【００６０】[0060]

【実施例１】ポリ乳酸系樹脂として融点が１３２．９℃
で、Ｄ−体含有率が８．４％、Ｌ−体含有率が９１．６
％で、メルトマスフローレイトが６．３ｇ／１０分のも
のを使用した。Example 1 A polylactic acid-based resin having a melting point of 132.9 ° C.
And the D-form content was 8.4% and the L-form content was 91.6.
%, And the melt mass flow rate was 6.3 g / 10 min.

【００６１】上記樹脂１００重量部に気泡調整剤として
タルク２．０部を混合し、この混合物を、一段目押出機
の口径が５０ｍｍ、二段目押出機の口径が６５ｍｍであ
るタンデム式押出機に投入した。二段目押出機のスクリ
ューは全長さにおいてフライトを有し、フライトが１８
０℃回転する毎にフライトの一部を切り込んだ押出機内
で樹脂を初め１５５℃に加熱して樹脂を溶融し、その後
樹脂温度を１７５℃まで上昇させ、この状態で、押出機
のバレルの途中から溶融樹脂にジメチルエーテルを１３
重量％の割合で圧入した。2.0 parts of talc as a cell adjuster was mixed with 100 parts by weight of the above resin, and the mixture was tandem type extruder having a first stage extruder having a diameter of 50 mm and a second stage extruder having a diameter of 65 mm. I put it in. The screw of the second-stage extruder has flights over its entire length,
The resin is first heated to 155 ° C in the extruder where a part of the flight is cut every time it rotates 0 ° C to melt the resin, and then the resin temperature is raised to 175 ° C, and in this state, in the middle of the barrel of the extruder. From molten resin to dimethyl ether 13
It was pressed in at a weight percentage.

【００６２】引き続き、押出機内で溶融樹脂を冷却し、
中心部分の樹脂温度を１１０．０℃、Ｄ／４部分の樹脂
温度を１１１．４℃としてフラット金型（口金間隙１．
２ｍｍ、口金幅８０ｍｍ、）から２４．８ｋｇ／ｈｒの
押出量で押し出した。その際二段目押出機のスクリュー
回転数は１０．８回転で、二段目押出機の溶融樹脂の平
均滞留時間は５２９秒であった。（押出機口径の二乗×
スクリュー回転数／押出量＝１．８）また口金部分の剪
断速度は３２６ｓｅｃ- 1 であった。Subsequently, the molten resin is cooled in the extruder,
The temperature of the resin in the central portion is 110.0 ° C and the temperature of the resin in the D / 4 portion is 111.4 ° C.
2 mm, die width 80 mm,) was extruded at an extrusion rate of 24.8 kg / hr. At that time, the screw rotation speed of the second-stage extruder was 10.8, and the average residence time of the molten resin in the second-stage extruder was 529 seconds. (Square of extruder diameter x
Shear rate of the screw rotational speed / extrusion amount = 1.8) The base part is 326Sec - 1.

【００６３】押出された発泡体は、口金の先端に密接に
取り付けられた２枚の板（幅５００ｍｍ、長さ４００ｍ
ｍ、内部に２０℃の冷却水を通水）を向きあわせてなる
偏向板を２対有する成形装置を通過させ、成形と同時に
冷却することにより板状発泡体に成形した。成形装置を
通過した直後の発泡体の表面温度は３５℃であった。The extruded foam had two plates (width 500 mm, length 400 m) closely attached to the tip of the die.
m, and passed through a molding apparatus having two pairs of deflecting plates each having cooling water of 20 ° C. facing each other, and cooled at the same time as molding to form a plate-shaped foam. The surface temperature of the foam immediately after passing through the molding apparatus was 35 ° C.

【００６４】得られた発泡体は均一に発泡しており、密
度が０．０３２ｇ／ｃｍ3 で連続気泡率は４．６％であ
った。また得られた発泡体の熱伝導率は０．０３３Ｗ／
ｍｋと、発泡剤としてフロンを全く使用することなくＪ
ＩＳ Ａ９５１１により規格化されている２種の熱伝導
率（０．０３４Ｗ／ｍｋ以下）に適合する値を示した。
また５％圧縮強度は０．１１ＭＰａ、圧縮弾性率は２．
３ＭＰａ、曲げ強度０．６５ＭＰａ、曲げ弾性率は０．
８５ＭＰａであった。The foam obtained was uniformly foamed, had a density of 0.032 g / cm 3 and an open cell ratio of 4.6%. The thermal conductivity of the obtained foam is 0.033 W /
mk and J without using CFC as a foaming agent at all
A value meeting the two types of thermal conductivity (0.034 W / mk or less) standardized by IS A9511 was shown.
The 5% compressive strength is 0.11 MPa and the compressive elastic modulus is 2.
3 MPa, bending strength 0.65 MPa, bending elastic modulus is 0.
It was 85 MPa.

【００６５】[0065]

【実施例２】ポリ乳酸系樹脂として融点が１４２．４℃
で、Ｄ−体含有率が４．４％、Ｌ−体含有率が９５．６
％で、で、メルトマスフローレイトが７．５ｇ／１０分
のものを使用した。[Example 2] Polylactic acid resin having a melting point of 142.4 ° C
Thus, the D-form content was 4.4% and the L-form content was 95.6.
%, And the melt mass flow rate was 7.5 g / 10 min.

【００６６】上記樹脂１００重量部に気泡調整剤として
タルク２．０部を混合し、この混合物を、実施例１で使
用した押出機に投入した。押出機内で樹脂を初め１６５
℃に加熱して樹脂を溶融し、その後樹脂温度を１８０℃
まで上昇させ、この状態で、押出機のバレルの途中から
溶融樹脂にジメチルエーテルを８重量％の割合で圧入し
た。引き続き、押出機内で溶融樹脂を冷却し、中心部分
の樹脂温度を１２９．１℃、Ｄ／４部分の樹脂温度を１
３０．３℃として実施例１と同じフラット金型から押し
出した。その際二段目押出機のスクリュー回転数は９．
６回転であった。（押出機口径の二乗×スクリュー回転
数／押出量＝１．６）押し出された発泡体は、口金の先
端に密接に取り付けられた２枚の板を向きあわせてなる
偏成形装置を通過させ、成形と同時に冷却することによ
り幅１８０ｍｍ、厚み２８ｍｍの板状発泡体に成形し
た。成形装置を通過した直後の発泡体の表面温度は３３
℃であった。2.0 parts of talc as a cell adjuster was mixed with 100 parts by weight of the above resin, and this mixture was put into the extruder used in Example 1. 165 resin in the extruder
Heat to ℃ to melt the resin and then increase the resin temperature to 180 ℃
Then, in this state, dimethyl ether was pressed into the molten resin at a rate of 8% by weight from the middle of the barrel of the extruder. Subsequently, the molten resin was cooled in the extruder, the resin temperature in the central portion was 129.1 ° C., and the resin temperature in the D / 4 portion was 1
It was extruded from the same flat mold as in Example 1 at 30.3 ° C. At that time, the screw rotation speed of the second-stage extruder was 9.
It was 6 revolutions. (Square of extruder diameter × screw rotation speed / extrusion amount = 1.6) The extruded foam is passed through an uneven molding device formed by facing two plates closely attached to the tip of the die, By cooling at the same time as the molding, a plate-like foam having a width of 180 mm and a thickness of 28 mm was molded. The surface temperature of the foam immediately after passing through the molding device is 33.
It was ℃.

【００６７】得られた発泡体は均一に発泡しており、密
度が０．１１ｇ／ｃｍ3 で連続気泡率は１８．２％、熱
伝導率は０．０３９Ｗ／ｍｋとＪＩＳ Ａ９５１１によ
り規格化されている１種の熱伝導率（０．０４０Ｗ／ｍ
ｋ以下）に適合する値を示した。また５％圧縮強度は
１．０ＭＰａ、圧縮弾性率は２４ＭＰａ、曲げ強度２．
８ＭＰａ、曲げ弾性率は２６ＭＰａと強度に優れた発泡
体であった。The obtained foam was uniformly foamed, had a density of 0.11 g / cm 3 , an open cell rate of 18.2%, and a thermal conductivity of 0.039 W / mk, which was standardized by JIS A9511. One type of thermal conductivity (0.040W / m
k or less). The 5% compressive strength is 1.0 MPa, the compressive elastic modulus is 24 MPa, and the bending strength is 2.
The foam was 8 MPa and had a flexural modulus of 26 MPa, which was excellent in strength.

【００６８】[0068]

【比較例１】ポリ乳酸系樹脂として融点が１７１．０℃
で、Ｄ−体含有率が１．６％、Ｌ−体含有率が９８．４
％、メルトマスフローレイトが８．４ｇ／１０分のもの
を使用し、この樹脂１００重量部に気泡調整剤としてタ
ルク２．０部を混合し、この混合物を、実施例１で使用
した押出機に投入した。押出機内で樹脂を初め１７０℃
に加熱して樹脂を溶融し、その後樹脂温度を１９０℃ま
で上昇させ、この状態で、押出機のバレルの途中から溶
融樹脂にジメチルエーテルを１０重量％の割合で圧入し
た。引き続き、押出機内で溶融樹脂を冷却し、中心部分
の樹脂温度を１４９．６℃、Ｄ／４部分の樹脂温度を１
５１．８℃として実施例１で使用した金型から押し出し
たが、金型から溶融樹脂が断続的に噴出し、安定した状
態で発泡体をつくることができなかった。[Comparative Example 1] Polylactic acid resin having a melting point of 171.0 ° C
And the D-form content was 1.6% and the L-form content was 98.4.
%, A melt mass flow rate of 8.4 g / 10 min was used, 100 parts by weight of this resin was mixed with 2.0 parts of talc as a cell adjuster, and the mixture was applied to the extruder used in Example 1. I put it in. Resin at 170 ° C in the extruder
Then, the resin temperature was raised to 190 ° C., and dimethyl ether was pressed into the molten resin at a rate of 10% by weight from the middle of the barrel of the extruder in this state. Subsequently, the molten resin was cooled in the extruder, the resin temperature in the central portion was 149.6 ° C., and the resin temperature in the D / 4 portion was 1
It was extruded from the mold used in Example 1 at 51.8 ° C., but the molten resin spouted intermittently from the mold and a foam could not be formed in a stable state.

【００６９】[0069]

【比較例２】中心部分の樹脂温度を１１５．２℃、Ｄ／
４部分の樹脂温度を１１６．４℃とした以外は実施例１
と同じ方法で板状発泡体をつくった。[Comparative Example 2] The resin temperature in the central portion was 115.2 ° C and D /
Example 1 except that the resin temperature of 4 parts was 116.4 ° C
A plate-like foam was prepared in the same manner as in.

【００７０】得られた発泡体は密度が０．０３４ｇ／ｃ
ｍ3 で、連続気泡率は２２．６％、熱伝導率は０．０４
１Ｗ／ｍｋとＪＩＳ Ａ９５１１により規格化されてい
る１種の熱伝導率（０．０４０Ｗ／ｍｋ以下）に適合せ
ず、断熱性に劣った発泡体であった。The foam obtained has a density of 0.034 g / c.
m 3 , open cell ratio is 22.6%, thermal conductivity is 0.04
The foam did not conform to 1 W / mk and one type of thermal conductivity (0.040 W / mk or less) standardized by JIS A9511, and was a foam having poor heat insulation.

【００７１】[0071]

【比較例３】発泡剤としてブタンを使用した以外は実施
例２と同じ方法で発泡体を試作した。その際の樹脂温度
は中心部分の樹脂温度が１２９．１℃、Ｄ／４部分の樹
脂温度が１３１．２℃であった。[Comparative Example 3] A foam was manufactured in the same manner as in Example 2 except that butane was used as the foaming agent. The resin temperature at that time was 129.1 ° C. at the central portion and 131.2 ° C. at the D / 4 portion.

【００７２】得られた発泡体は密度が０．１１ｇ／ｃｍ
3 で連続気泡率は２４．２％、熱伝導率は０．０４２Ｗ
／ｍｋとＪＩＳ Ａ９５１１により規格化されている１
種の熱伝導率（０．０４０Ｗ／ｍｋ以下）に適合せず、
断熱性に劣った発泡体であった。The obtained foam has a density of 0.11 g / cm.
3 , open cell rate is 24.2%, thermal conductivity is 0.042W
/ Mk and standardized by JIS A9511 1
Does not conform to the thermal conductivity of seeds (0.040 W / mk or less),
The foam was inferior in heat insulation.

【図面の簡単な説明】[Brief description of drawings]

【図１】この発明において、樹脂温度を測定するために
付設した熱電対のブレーカープレート上の位置を示す。FIG. 1 shows the position on a breaker plate of a thermocouple attached to measure a resin temperature in the present invention.

───────────────────────────────────────────────────── フロントページの続き Ｆターム(参考） 4F074 AA68 AB03 BA75 CA22 DA02 DA13 DA32 4J200 AA06 BA14 CA09 DA16 EA11   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4F074 AA68 AB03 BA75 CA22 DA02                       DA13 DA32                 4J200 AA06 BA14 CA09 DA16 EA11

Claims (3)

【特許請求の範囲】[Claims] 【請求項１】 乳酸のＤ−体とＬ−体とが、そのうちの
一方が２〜１０％で他方が９８〜９０％の割合に共重合
して、１１０〜１７０℃の融点を持つポリ乳酸系樹脂か
らなる発泡体であって、見掛け密度が０．１２ｇ／ｃｍ
3 以下であり、連続気泡率が２０％以下であることを特
徴とする、遺棄分解性の良好な軽量構造材。1. A polylactic acid having a melting point of 110 to 170 ° C., which is obtained by copolymerizing a D-form and a L-form of lactic acid such that one of them is 2 to 10% and the other is 98 to 90%. It is a foam made of resin and has an apparent density of 0.12 g / cm.
A lightweight structural material having good abandonment degradability, which is 3 or less and has an open cell ratio of 20% or less. 【請求項２】 乳酸のＤ−体とＬ−体とが、そのうちの
一方が２〜１０％で他方が９８〜９０％の割合に共重合
して、１１０〜１７０℃の融点を持つポリ乳酸系樹脂か
らなる発泡体であって、見掛け密度が０．１２ｇ／ｃｍ
3 以下であり、連続気泡率が２０％以下であることを特
徴とする、遺棄分解性の良好な断熱材。2. A polylactic acid having a melting point of 110 to 170 ° C., which is obtained by copolymerizing the D-form and the L-form of lactic acid, one of which is 2 to 10% and the other of which is 98 to 90%. It is a foam made of resin and has an apparent density of 0.12 g / cm.
A heat insulating material having good abandonment degradability, which is 3 or less and has an open cell ratio of 20% or less. 【請求項３】 乳酸のＤ−体とＬ−体とが、そのうちの
一方が２〜１０％で他方が９８〜９０％の割合で共重合
したものであって、１１０〜１７０℃の融点を持つポリ
乳酸系樹脂を押出機内で溶融し、これに発泡剤として上
記融点より低い沸点を持った脂肪族エーテルを樹脂に対
して０．５重量％以上含ませ、得られた発泡剤含有の溶
融樹脂を、樹脂の融点と融点より４０℃だけ低い温度と
の間の温度で押出機から押し出して発泡させることを特
徴とする、遺棄分解性の良好な軽量構造材の製造方法。3. D- and L-forms of lactic acid, one of which is 2 to 10% and the other of which is 98 to 90%, having a melting point of 110 to 170 ° C. Melt the polylactic acid-based resin in the extruder and add 0.5 wt% or more of the aliphatic ether having a boiling point lower than the above melting point as a foaming agent to the resin as a foaming agent. A method for producing a lightweight structural material having good abandonable decomposability, which comprises extruding a resin at a temperature between a melting point of the resin and a temperature lower than the melting point by 40 ° C. to foam the resin.
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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2010023333A (en) * 2008-07-18 2010-02-04 Sekisui Plastics Co Ltd Container forming poly-lactic acid resin foaming particle and its production process, also production process of poly-lactic acid resin foam container using container forming poly-lactic acid resin foaming particle
JP2012531549A (en) * 2009-06-29 2012-12-10 サンゴバン イゾベール アーベー Auxiliary insulation system and method for insulating a facade
JP2014177791A (en) * 2013-03-14 2014-09-25 Dow Chemical Company Lightweight banking
EP4361206A1 (en) 2022-10-31 2024-05-01 Ricoh Company, Ltd. Polylactic acid resin composition, foamed polylactic acid resin, method of manufacturing foamed polylactic acid resin, and product

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB201501834D0 (en) * 2015-02-04 2015-03-18 Isis Innovation An impact absorbing structure

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2010023333A (en) * 2008-07-18 2010-02-04 Sekisui Plastics Co Ltd Container forming poly-lactic acid resin foaming particle and its production process, also production process of poly-lactic acid resin foam container using container forming poly-lactic acid resin foaming particle
JP2012531549A (en) * 2009-06-29 2012-12-10 サンゴバン イゾベール アーベー Auxiliary insulation system and method for insulating a facade
JP2014177791A (en) * 2013-03-14 2014-09-25 Dow Chemical Company Lightweight banking
EP4361206A1 (en) 2022-10-31 2024-05-01 Ricoh Company, Ltd. Polylactic acid resin composition, foamed polylactic acid resin, method of manufacturing foamed polylactic acid resin, and product

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